1. Field of the Invention
The invention relates to a direct injection spark ignition internal combustion engine, and a fuel injection control method for the same.
2. Description of the Related Art
In conventional direct injection spark ignition internal combustion engines equipped with fuel injection valves, which inject fuel into the combustion chambers, and that perform the homogeneous combustion, the intake valves may be closed after the gas in the combustion chamber begins to flow backward into the intake passageway via the intake valve after the start of the compression stroke, and inject fuel after the intake valve closes (see Japanese Patent Application Publication No. 9-287487 (JP-A-9-287487)). According to this internal combustion engine, because the intake valve of each combustion chamber is closed after the gas in the combustion chamber begins to flow back into the intake passageway via the intake valve after the start of the compression stroke, pumping loss and fuel consumption are reduced. Furthermore, because fuel is injected after the intake valve is closed, the temperature and the pressure at and near top dead center can be made higher than if fuel is injected when the intake valve is open, so that a strong turbulence will advantageously occur, and therefore will improve the combustion rate.
However, in this internal combustion engine, because the time from fuel injection to ignition is short, uniform mixture in the combustion chamber, which is optimum to the homogeneous combustion, cannot be obtained, thus giving rise to a problem of increase of unburned fuel loss, such as increase of unburned fuel, and the like.